It is proposed to ulitize concepts derived from research studies undertaken on HL-14644 to develop and evaluate new circulatory assist systems which provide supplemental perfusion to critically underperfused acutely ischemic myocardium and effectively unload the dysfuntioning left ventricle (LV). Prior experimental studies led to criteria which can be applied to all modes of counterpulsation, but revealed limitations of current systems in terms of inadequate perfusion of severely deficient regions following acute coronary occlusions. In view of the need for early and effective intervention before irreversible morphologic alterations have set in, emphasis is placed on developing an assist capable of salvaging jeopardized regions of the heart. It now appears that a new system of regional Synchronized Retroperfusion (SRP) constitutes the optimal approach to diastolic augmentation of acutely ischemic tissue perfusion, and is suitable for combination with maximal counterpulsation systolic sink LV unloading. SRP provides direct retrograde oxygen and substrate supplementation or drug treatment to the injured cardiac zone while facilitating essential coronary venous drainage. Based on preliminary encouraging experimental data and study of human coronary venous vasculature, further research and development of SRP and its combination with counterpulsation is planned to clarify mechanisms and verify effectiveness, safety, simplicity and prompt operability. Limited checks indicate the potential of another concept in which a simple balloon tipped catheter is placed in the ascending aorta to maximize counterpulsation diastolic augmentation of the aortic root pressure for enhanced acute delivery of blood to underperfused ischemic zones through coronary collaterals. This proposed approach can also be applied for phased drug infusions directly into the coronary vasculature. It is planned to utilize new echocardiographic, tagged microspheres and morphologic methodologies for assessment of regional as well as global myocardial consequences of the proposed systems. The combined circulatory assist will provide alternatives, including emphasis on cardiopulmonary unloading and/or acute supplementation of nutrition to critically jeopardized myocardium.